The effect of internalizing symptomatology on executive functioning performance and processing speed in children with ADHD

Attention Deficit Hyperactivity Disorder (ADHD) is one of the most common childhood psychological disorders with prevalence estimates ranging from 3%-7% (APA, 2000) and one of the most thoroughly studied child neurocognitive disorders. Children with ADHD have consistently shown executive functioning and processing speed deficits on a variety of measures (Berlin, Bohlin, Nyberg, & Janols, 2004; Geurts, Verté, Oosterlaan, Roeyers & Sergeant, 2004; Nigg, 1999; Nigg, Blaskey, Huang-Pollock & Rappley, 2002). The research on executive functioning deficits in other childhood disorders has been comparatively lacking. There is some research that suggests that internalizing disorders, such as anxiety and depression, can also have a detrimental effect on certain executive functioning domains (Airaksinen, Larsson, & Forsell, 2005; Christopher, & MacDonald, 2005; Emerson, Mollet, & Harrison, 2005). It is unclear how these internalizing symptoms will impact executive functioning, processing speed and fine motor control in children with ADHD.
The purpose of this study is to determine whether the presence of internalizing symptoms impacts the ability of children with ADHD to perform executive functioning, processing speed, and fine motor control tasks. In order to assess this, the predictive ability of gender, ADHD subtype, parent ratings of anxiety, and parent ratings of depression were examined for processing speed, working memory, response inhibition, vigilance and fine motor control tasks. Gender was found to predict differences in working memory, response inhibition and fine motor control. ADHD subtype was found to predict differences in response inhibition. Parent ratings of anxiety were found to interact with ADHD subtype to predict some aspects of vigilance. Parent ratings of anxiety and of depression were found to predict differences in other aspects of vigilance looking across gender and subtype. Finally, teacher ratings of anxiety were found to predict differences in working memory.